The present invention relates to the field of warp beams made of light tubular metallic material which are used for warping, section warping or winding threads of textile material (e.g., cotton) or polymeric/copolymeric thermoplastic melt-spun material (e.g., polyethylene, polypropylene).
As thread is wound upon warping beams to form thread packages the warp beams are subjected to traction forces and bending stresses during winding which cause undesired warp beam deflection. The latter occurs even if the warp beam is made to exacting tolerances. However, during the manufacture of warp beams exacting tolerances are not maintained simply because of the manner in which conventional warp beams are constructed. Normally the conventional warp beams are constructed from an aluminum tube which is generally produced by drawing, rolling or the like, and these processes alone create undesired tolerances primarily resulting from normal hardening of the metal as it is being formed. Moreover, though it is desired to form the tube to a perfectly circular shape, deviations therefrom occur, and most tubes are slightly oval and are also deformed along their axes (sword effect). These tolerance deviations are not negligible, and manufacturers have attempted to combat the same by using considerably oversized metal for forming the tubes of the warp beam. However, the greater the thickness of the tube, the more expensive the eventually formed warp beam and the greater the deviation from desired tolerances during formation.
For example, a purchaser/user of a warp beam requires a minimum tube wall thickness and this tube wall thickness must be maintained within desired tolerances. Obviously, each tube is desirably perfectly circular in cross-section and should also be perfectly axially straight, although in practice deviations obviously occur. However, if one begins with relatively thick tube wall thickness there is a possibility that the overall tolerances might be closer to desired tolerances but this is achieved only at the desired factor of increased cost because of the increased tube wall thickness.
The warp beam also has flanges at the ends of the tube and obviously the flanges must be so mounted that their axes are coaxial to effect symmetrical rotation of the warp tube. If the tube is not perfectly round or not perfectly straight, coaxial alignment between the flanges will not be effected by simply inserting centering collars of the flanges into the interior of the tube ends. For example, if the tube is slightly elliptical, the orientation of the ellipse at axially opposite ends of the tube is not necessarily the same and might be slightly peripherally/circumferentially offset. Thus, when collars of the flanges are inserted into these tube ends they self-center to the configuration of the internal elliptical surface of the tube, and if these internal elliptical surfaces are not perfectly longitudinally symmetrical, the axes of the flanges will not be coaxial. Because of the latter it has been the practice to machine or hollow-out the inner peripheral surface of each tube end to a diameter larger than the inside diameter of the raw-sized tube and generally correspondingly match the outside cylindrical surface of the collar of the flange fitted therein. Obviously this machining operation thinned the wall thickness at tube ends which creates a weakening point at the connection thereof with the associated flanges. Normally the connection is by way of a circumferential weld and since there is less wall material at the tube ends, the weld cannot be as strong as it might be if the wall thickness was not reduced. Hence, in those cases where the tube ends are machined to create a cylindrical internal surface as perfectly circular as possible, one must begin with a relatively thick raw-sized tube so that the wall thickness remaining after machining will not unduly weaken the eventually formed warp beam and will maintain desired predetermined manufacturing tolerances.